Reproductive potential of the parasitic wasp Microplitis rufiventris Kok. reared in hosts treated with the growth regulator precocene II

The reproductive potential of Microplitis rufiventris Kok. females resulted from Spodoptera littoralis (Boisd.) larvae topically treated by a constant dose (70 pg/5 pl) of the growth regulator precocene II at different intervals of post-parasitism was studied in the laboratory. The obtained results showed that the effects of PH vary according to the timing of treatment relative to larval development of the parasitoid. Reduction in reproductive capacity of the parasitoid occurred when PII was applied on host larvae containing young parasitoid larvae. Workers should be aware from the delayed effects of precocenes which may occur in later stages of the non-target insects.     

Über Eignung und Reaktion überwinternder und aktiver Raupen von Sesamia cretica Led. (Lepid., Noctuidae) in bezug auf den Parasitoiden Bracon brevicornis Wesm. (Hymen., Braconidae)

Laboratory studies were undertaken to determine the differential response and suitability of 2 types of host larvae ofSesamia cretica (hibernating and active) to the development of the braconid,B. brevicornis. The parasitoid was able to immobilize the 2 forms of larvae. However, hibernating larvae were significantly less sensitive to the parasitoid's venom than active larvae. Parasitoid parents (specially females) which associated with hibernating larvae were significantly longer-lived than those kept with active larvae. Life cycle period of the parasitoid did not affect with any of the 2 types of larvae. However, numbers of each of cocoons and emerged adults/larva were significantly higher in case of hibernating than in case of active larvae. Moreover, the produced adults from hibernating larvae were significantly larger in their size. Therefore the hibernating host larvae will serve better for mass colonization of this braconid.     

Über die Fähigkeit vonBracon brevicornis Wesm. (Hym., Braconidae), zwischen nicht infizierten und von Bakterien infizierten Raupen vonSesamia cretica Led. (Lep., Noctuidae) zu unterscheiden

Sesamia cretica larvae infected with the bacterium,Serratia marcescens orBacillus thuringiensis were exposed toBracon brevicornis females, separately and in combination with non-infected larvae in the laboratory. Host larvae were exposed to the parasitoid under two manipulations “the larvae still alive or dead completely”. Bracon brevicornis females could not absolutely discriminate between healthy and moribund larvae (due toB. t. orS. m.) when those larvae exposed in a live appearance separately or jointly. However, they could discriminate between dead larvae (due to parasitoid's venom) and dead larvae due to Bacteria (B. t. orS. m.).     

Host discrimination ability in the tephritid parasitoid Psyttalia concolor (Hymenoptera: Braconidae)

Psyttalia concolor (Szépligeti) (Hymenoptera: Braconidae) is a koinobiont larval-pupal endoparasitoid of many Tephritidae of economic importance. Little has been reported on the ability of females to discriminate between healthy and parasitized hosts, as well as parasitized versus superparasitized larvae. Two-choice bioassays were conducted to evaluate the preferences of P. concolor naïve females for healthy or single-parasitized/superparasitized C. capitata larvae, as well as the host discrimination ability among medfly larvae which had been superparasitized by the same wasp or by a conspecific one. Psyttalia concolor preferred to oviposit in a unparasitized C. capitata larva than in a self-parasitized one. Females also showed an innate ability to discriminate between larvae parasitized twice or only once, preferring the latter. This ability helps the female to optimise its oviposition decisions by deliberately avoiding superparasitized hosts, since it is known that they give a lower return in offspring number and quality than do singly parasitized hosts. Our findings contribute to a better knowledge of the P. concolor host location behaviour and also to improve its mass-rearing technique through a rational management of the host/parasitoid ratio and the host exposure time. Indeed, the proper setting of these parameters allows to reduce the fraction of single-parasitized and heavily superparasitized larvae and to enhance P. concolor rearing in terms of parasitoid offspring.     

Zur Wirkung von Precocen 2 und Fenarimol auf die Kohlblattlaus,Brevicoryne brassicae (L.) und ihren ParasitoidenDiaeretiella rapae (M'Intosh)

The anti-hormone compounds, precocene-2 (anti-juvenile hormone) and fenarimol (anti-ecdysone) were evaluated against the green cabbbage aphid,Brevicoryne brassicae (L.) alone and for their compatibility with the endoparasiteDiaeretiella rapae (M'Intosh). The results revealed that precocene-2 provided more than 90% control ofB. brassicae acted on larvae within 72 h after the treatment, while fenarimol was less effective. Moreover, either precocene-2 or fenarimol extremely reduced the reproductive potentiality ofB. brassicae surviving adults. Both anti-hormone compounds demonstrated compatibility withD. rapae, a parasitoid ofB. brassicae. No considerable difference was detected when parasite emergence was compared from treated and untreated individuals.     

Laboruntersuchungen zur Wirtshabitat-Wahl von Bracon brevicornis Wesm. (Hym., Braconidae), einem Parasitoiden der Raupen von Sesamia cretica Led. (Lep., Noctuidae) in Sorghum-Stengeln

Females of the parasitoid,Bracon brevicornis were more strongly attracted to “live” larvae ofSesamia cretica (themselves) than any other accessible materials (e. g. “stalk”, “frass”, “paralyzed larva” or control). They were also attracted to paralyzed larvae but only when live larvae were absent. On the other hand, males were more strongly attracted to “stalk” than to “live” larvae or any other available material. Apparently “stalk” exhibited an important cue that directed the parasitoid males.     

Biology of two key Palaearctic larval ectoparasitoids when parasitizing the invasive pest Tuta absoluta

During the last few years following the invasion of European tomato crops by the invasive South American tomato leafminer, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), several indigenous larval parasitoid species were recorded as natural enemies of this pest. Necremnus cf. artynes (Walker) and to a lesser extent Stenomesius sp. nr. japonicus (Ashmead) (Hymenoptera: Eulophidae) have been frequently reported attacking T. absoluta in tomato greenhouses in Europe and they are considered as possible biocontrol agents. Few biological data are available on these two species, notably when they parasitize T. absoluta. Therefore, the present study documents their biology when parasitizing T. absoluta, and provides scientific bases for potential development of biological control programs relying on larval ectoparasitoids in invaded areas. We demonstrated the ability of the two parasitoid species to reproduce on T. absoluta as host on tomato plants. On average, N. cf. artynes female parasitized 28.5 larvae and killed 26.2 larvae during its life time whereas S. sp. nr. japonicus female was more long-lived and consequently more efficient; it parasitized 144.3 larvae and killed 90.1 larvae. In a second step, we also explored the effect of T. absoluta larvae instar on parasitism by S. sp. nr. japonicus and subsequent development of the parasitoid offspring. Best results were obtained with the third larvae instar with a higher number of offspring produced, bigger individuals and a higher proportion of females. Our results support the hypothesis that the two species are good candidates for biological control programs targeting T. absoluta in Europe.     

For sex and more: attraction of the tephritid parasitoid Psyttalia concolor (Hymenoptera: Braconidae) to male sex pheromone of the olive fruit fly,Bactrocera oleae

The braconid parasitoid Psyttalia concolor foraging for larvae of Bactrocera oleae (Diptera: Tephritidae) uses olfactory cues from the larval microhabitat. However, it could rely on the sex pheromones of adults of its host, since B. oleae mating leks usually occur on olive plants and a high number of infested fruits can be easily located in their close proximity. We quantified the behavioural responses of P. concolor towards different doses of the two major sex pheromone components of B. oleae, the female-borne 1,7-dioxaspiro[5.5]undecane (DSU) and the male-borne (Z)-9-tricosene (ZT). Results showed that P. concolor females and males were attracted only to the highest amounts of ZT (10 B. oleae male equivalents), regardless of the mating status. Wasps remained longer on the surfaces treated with high ZT amounts over the control. P. concolor females could exploit the ZT produced by lekking olive fruit fly males as a foraging kairomone. This could allow them to rapidly track B. oleae-infested olive plants, thus raising their chances to locate host larvae during their lifespan. On the other hand, the perception of ZT by P. concolor males could raise their chances to locate receptive females emerging from parasitised B. oleae pupae or also ovipositing in olive fruits. This study increases the knowledge of the reproductive biology of P. concolor, highlighting a case of chemical espionage in which a sex pheromone component from adult stages of the host is exploited both as a foraging kairomone by female parasitoids and as a sexual kairomone by male wasps.     

Wirkungen zwischen Bacillus thuringiensis Berl. und Larven der Schlupfwespe Bracon brevicornis Wesm. in bzw. an den Raupen von Sesamia cretica Led. bei verschiedenen Temperaturen

Laboratory trials were undertaken to investigate the interactions which may occur when rearing the parasitoid,Bracon brevicornis on Sesamia cretica larvae after being injected with the pathogen,Bacillus thuringiensis under 5 constant temperatures. Bacillus-infected larvae ofS. cretica had detrimental effects on the parasitoid's progeny e. g. prolonged periods of both cocoon stage and total development at 20 or 25 °C; and decreased number of formed cocoons or produced adults at all tested temperatures. The most deleterious temperature for the parasitoid rearing under condition of the bacterial pathogen was 30 or 35 °C.     

Impact of neem and chinaberry fruit extracts on the pest/parasitoid (Pieris rapae/Hyposoter ebeninus) interactions

A new technique was performed to simulate exposure of the host Pieris rapae larvae to both botanical treatment and the parasitoid Hyposoter eheninus in different sequences. It was found that: host larvae subjected to both parasitoid and 1?% neem treatment showed significant or insignificant reductions both in pupal formation as well as adult emergence percentages when treatment preceded or followed parasitism, respectively. Both neem treatments revealed significant prolongation in the development of unparasitized and parasitized larvae (on average 4 to 5 days delay), whereas chinaberry caused significant prolongation only among parasitized larvae (on average 2.7 days delay in egg-larval duration). Fate of parasitism among untreated hosts was found to be faster than among neem-treated ones. Parasitism percentages among 1 and 0.5?% neem-treated third instar host larvae held 7 days before parasitism reached 3 and 2 times that achieved among those reared on untreated diet for the same period, ­respectively. It was concluded that prolongation of the preferred target instars of the host, due to neem treatments, increased the chance for parasitism. Nevertheless, treatment with neem at the LC₅₀ level exhibited a great reduction in parasitoid progeny. However, a lower concentration (LC₂₅) could reasonably potentiate parasitism without drastic losses in parasitoid emergence.     

Altägyptische Fliegen- und Käferrelikte in einem Priestersarg der achtzehnten Dynastie

Ancient Egyptian insect relics were accidentally enclosed in embalming resin which leaked from a priest's mummy and solidified on the floor of a wooden coffin from the end of the XVIII^th Dynasty (presumably 1323?–?1295 BC). The preserved insect relics were blowflies (Calliphoridae) recognized as Chrysomya marginalis or Chrysomya megacephala whose larvae had developed by feeding on the deceased's body prior to mummification as well as furniture beetles (Anobiidae) being either Oligomerus ptilinoides or Priobium carpini whose larvae had ingested the coniferous wood of the coffin. It is most likely that the human corpse and coffin were first attacked by the blowflies and furniture beetles prior to embalming, while infestation of the insect remains and textiles by Anthrenus sp. (Dermestidae) occurred in our time.     

Übertragung zweler bakterieller Pathogene in den Körper von Sesamia cretica Led. (Lep., Tortricidae) mittels des Legebohrers von Bracon brevicornis Wesm. (Hym., Braconidae)

Laboratory trials were undertaken to investigate the transmission of 2 bacterial pathogens (Serratia marcescens Bizio andBacillus thuringiensis Berliner) by the ovipositor of a braconid parasitoid,Bracon brevicornis Wesmael into the body cavity ofSesamia cretica Lederer. The braconid's ovipositor was able to transmit the 2 bacterial pathogens and plays as inoculating needle. The host larvaeS. cretica were significantly immobilized faster by the contaminated ovipositor of a parasitoid (in case of the 2 pathogens). After successful transmission of the bacterial pathogen into the body cavity of host larvae, different deleterious effects were significantly found for the parasitoid and its progeny specially in case ofS. marcescens. Through contamination of the ovipositor, the non-sporeforming bacterium,S. marcescens has more pathogenic effects on the parasitoid and its progeny than the sporeforming bacterium,B. thuringiensis.     

补充营养对白蜡吉丁肿腿蜂寄生效率和发育进程的影响

[目的]为了探明补充营养是否对白蜡吉丁肿腿蜂雌蜂的寄生效率、生殖能力和寿命有显著影响。[方法]本文通过在白蜡吉丁肿腿蜂搜寻到寄主前期为其提供寄主血淋巴和蜂蜜补充营养,调查有前期补充营养经历的肿腿蜂对寄主麻天牛的寄生率、母蜂生殖能力和子代蜂发育进程的变化。同时,给予刚羽化的肿腿蜂雌蜂短期的补充营养的过程,调查其寿命长短的变化情况。[结果]研究结果表明,寄主血淋巴和糖类物质均可以作为供肿腿蜂补充营养的潜在食物源。寄生前期取食寄主血淋巴和蜂蜜的肿腿蜂寄生率显著高于前期仅补充蒸馏水的个体。补充营养后可促使寄生蜂卵的成熟,可以使肿腿蜂更快的开始产卵进程。前期取食寄主血淋巴的肿腿蜂生殖能力显著高于寄生前期仅补充蒸馏水的个体,取食蜂蜜的肿腿蜂产卵量较前2组均无显著差异。寄生蜂母蜂是否补充营养对其子代的发育过程和性比无显著影响。此外,生存分析结果表明,刚羽化的肿腿蜂补充营养后,其寿命显著延长。取食寄主血淋巴或蜂蜜的寄生蜂寿命均约为羽化后无营养补充经历雌蜂个体的2倍。[结论]以上结果表明,白蜡吉丁肿腿蜂在寄生过程开始前期的补充营养过程可以显著的增强其对寄主害虫的控制作用和延长其寿命。取食蜂蜜或寄主血淋巴对肿腿蜂生殖和寿命的增强作用相近。建议在害虫的生物防治中,可以通过在天敌释放区周边配植一定的蜜源植物以此实现对天敌昆虫资源更有效的利用和保护。     

Mass rearing of <Emphasis Type="Italic">Neochrysocharis formosa</Emphasis> (Westwood) (Eulophidae: Hymenoptera), a parasitoid of leafminers (Agromyzidae: Diptera)

A method for mass rearing the parasitoid Neochrysocharis formosa (Westwood) was developed, using the leafminer Liriomyza huidobrensis (Blanchard) as insect host, and the Phaseolus vulgaris L. bean as host plant. About 1,500 parasitoids per tray of 84 plants emerged from about 2,000 leafminer larvae; 70% of these were females. The most suitable release density of host was two pairs of leafminer adults per bean plant, and that of parasitoid was three pairs per 24 leafminer larvae. Adult parasitoids were harvested based on positive photo-tactic response with 94.5% efficiency. Plants were improved by trimming their tips to increase the leaf area. The trimming process increased the number of leafminer larvae by about 32%. Furthermore, nitrogen fertilization of plants overcame the size reduction of the insects due to continuous rearing. Rearing of leafminer under light—dark (16:8 h) cycle decreased the development period of larvae and pupae. In addition, it restricted the time and duration of larval emergence and adult eclosion. Storage of parasitoid males and females at 7 and 10°C ± 0.5, respectively, proved to be optimal. The fertility of the mass-produced parasitoids after 1 year of rearing reduced by about 23%, and the sex ratio shifted toward males. In conclusion, successful mass production of N. formosa was achieved through designing suitable rearing cage and an efficient harvesting device, improving the host plant, and determining the age and the conditions for cold storage of the parasitoid and its host. Next, we checked the characteristics of the mass-produced wasps to ensure the efficacy when used in the field.     

Parasitism byMeteorus rubens onAgrotis ipsilon as affected by supplementary food and kairomone, field studies

Field experiments in clover field showed that releasing of 10 matedM. rubens females/m², increased parasitism amongA. ipsilon larvae from 16.7% at 0 to 43,3% after 10 days. Also, releasing 10 females/m² after spraying 3% molasses in tomato field increased parasitism from 4% at 0-day to 27.5% after 10 days amongA. ipsilon larvae. Spraying molasses and kairomone together on maize plants, increased markedly the rate of parasitism amongS. cretica larvae comparing with parasitism obtained when each of them was sprayed alone. The release ofM. rubens in a rate of 10 females/m² after spraying molasses and kairomone induced a significant increase in the rate of parasitism amongS. cretica larvae after 10 and 15 days compared to releasing 3 or 4 females of the parasitoid. A significant increase in parasitism amongS. cretica larvae on tomato after 10 and 15 days was recorded whenM. rubens was released at the rates of 5 and 10 females/m², after spraying molasses and kairomone, compared to other treatments.     

Reproduction of the parasitoids Anisopteromalus calandrae (Howard) and Lariophagus distinguendus (F?rster) on arenas containing a mixed population of the coleopteran pests Sitophilus oryzae and Rhyzopertha dominica

In this article, we assessed the reproduction rates of the generalist pteromalid parasitoids Anisopteromalus calandrae and Lariophagus distinguendus on the coleopteran pest species, Sitophilus oryzae and Rhyzopertha dominica, when these hosts were offered together under environmental conditions reproducing spring or early summer. These species had proved to be the most suitable hosts in terms of parasitoid progeny production for both parasitoid species in no choice experiments in previous studies. Trials with A. calandrae and L. distinguendus had lower pest emergence in the parasitoid treatment when compared to the control for S. oryzae. However, for R. dominica, there was no difference between treatments for either parasitoid species. Pest reduction levels reached by the two parasitoids were caused by parasitism effects together with other parasitoid-induced mortality causes, which included host feeding and unsuccessful parasitism. The most preferred host under the conditions tested for both parasitoid species was S. oryzae. The parasitoid L. distinguendus decreased grain loss significantly more than A. calandrae thanks to a greater reduction of pest population. Product loss in terms of reduction of the medium (brown rice) weight was always higher in the control treatments.     

松褐天牛肿腿蜂对松褐天牛低龄幼虫控制作用的研究

研究测定了松褐天牛肿腿蜂对松褐天牛1～3龄幼虫的控制作用,采用林间和室内罩网相结合的方法研究了2组松褐天牛肿腿蜂对松褐天牛幼虫的寄生情况.结果显示:在室内试验条件下,松褐天牛肿腿蜂产卵之前的刺蛰、补充营养取食能直接造成松褐天牛1～3龄幼虫死亡,对1、2及3龄幼虫的平均致死率分别为95.66％、85.91％、57.88％,并可产卵寄生2、3龄幼虫;林间释放2组松褐天牛肿腿蜂后,在刺蛰和补充营养取食后能有效寄生寄主的肿腿蜂雌蜂数量比例变化较大,有效肿腿蜂率最高为14.9％,最低为2.3％.松褐天牛肿腿蜂寄生行为不受寄主聚集程度的影响,但刚羽化出茧肿腿蜂雌蜂的寄生效率比经饲喂后的雌蜂高近5倍.从肿腿蜂单一个体来看,每头雌蜂补充营养取食和产卵寄生致死的松褐天牛幼虫数为2.1～7.7头.松褐天牛肿腿蜂雌蜂的补充营养习性及刺蛰、取食致死寄主行为在防治中有很重要的作用,表明该种肿腿蜂是防治松褐天牛的重要天敌,在生物防治松褐天牛幼龄幼虫上具有良好的应用前景.     

Effects of water stress on emission of volatile organic compounds by <Emphasis Type="Italic">Vicia faba</Emphasis>, and consequences for attraction of the egg parasitoid <Emphasis Type="Italic">Trissolcus basalis</Emphasis>

When plants are damaged by herbivorous insects, blends of volatile organic compounds (VOCs) are induced and released and can also be used by parasitoids to locate hosts. The aim was to determine whether VOCs induced by water stress affect the plant–herbivore–parasitoid system represented by broad bean (Vicia faba; Fabales: Fabaceae) stink bug (Nezara viridula; Heteroptera: Pentatomidae) egg parasitoid (Trissolcus basalis; Hymenoptera: Platygastridae). The effects of water stress (expressed as the percentage fraction of transpirable soil water [FTSW] supplied) alone and in combination with N. viridula damage (feeding plus oviposition) were determined according to: (1) the behavioural response of the egg parasitoid in a Y-tube olfactometer and (2) the plant VOCs collected and analysed by thermal desorption–gas chromatography–mass spectrometry. With pot water capacity as FTSW₁₀₀, water stress was applied as mild (FTSW₈₀), moderate (FTSW₅₀) and severe (FTSW₁₀). Bioassays with plants under abiotic stress alone showed that egg parasitoids are more attracted by FTSW₁₀ plants than by well-watered plants. When plants were under abiotic and biotic stress interactions, the egg parasitoids are more attracted by FTSW₁₀ and FTSW₅₀ plants than by well-watered plants infested with N. viridula. Considering VOCs emissions, projection to latent structures discriminant analysis (PLS-DA) separated treatments according to egg parasitoid responses. Water stress alone and in combination with biotic stress induced changes in VOC emissions of V. faba plants that attract egg parasitoids. These findings contribute to our understanding of how water stress affects the interactions between plants, insect pests and egg parasitoids.     

寄主树木、寄主和环境因子对松褐天牛深沟茧蜂寄生率的影响研究

[目的]松材线虫病是我国对森林危害和威胁最严重的病害,控制其传播媒介昆虫松褐天牛是防治松材线虫病的主要手段。作者发现的松褐天牛深沟茧蜂(Iphiaulax monochamusi Yang)是寄生松褐天牛中老龄幼虫的重要天敌。为明确松褐天牛深沟茧蜂的寄生率与寄主树木、寄主和环境因子的关系,开展了本研究。[方法]通过解剖46株松褐天牛危害致死的马尾松,调查了松褐天牛深沟茧蜂寄生率与马尾松、松褐天牛和环境因子之间的关系。[结果]调查研究表明:寄主树木的高度、胸径和树龄对松褐天牛深沟茧蜂寄生率没有显著影响,松褐天牛的数量对松褐天牛深沟茧蜂寄生率亦没有显著影响,而松褐天牛幼虫龄期和松褐天牛幼虫在树干上的位置显著影响松褐天牛深沟茧蜂寄生率。松褐天牛深沟茧蜂寄生率与松褐天牛龄期呈显著正相关,其偏好寄生3~5龄幼虫;就天牛在其危害寄主树木上的位置而言,松褐天牛深沟茧蜂偏好寄生马尾松主干上部和在韧皮部危害的松褐天牛幼虫,其对位于马尾松树干上部的寄主幼虫寄生率最高,达27.38%,对在韧皮部生活、危害的寄主幼虫寄生率为20.18%,显著高于位于木质部生活的寄主幼虫寄生率(5.46%)。逐步回归分析表明:影响松褐天牛深沟茧蜂寄生率的关键环境因子是寄主树木的坡位和其它天敌寄生率,其中,坡位与松褐天牛深沟茧蜂呈显著正相关,其它天敌寄生率与松褐天牛深沟茧蜂寄生率呈显著负相关。[结论]以上研究初步明确了松褐天牛深沟茧蜂的寄生率与寄主树木、寄主害虫和天敌之间的关系,为今后利用该重要天敌控制松褐天牛打下了基础。     

Beziehungen zwischen dem Bakterium Serratia marcescens (Biz.) und der in den Raupen von Sesamia cretica. Led. (Lep., Tortricidae) sich entwickelnden Schlupfwespe Bracon brevicornis Wesm. (Hym., Braconidae)

Laboratory experiments were undertaken to study the interrelationships which may be detected when rearing the ectoparasitoid,Bracon brevicornis onSesamia cretica larvae after being injected with the bacterial pathogen,Serratia marcescens at five constant temperatures. Many effects detrimental to the parasitoid were found through rearing onSerratia-infected larvae ofSesamia e.g. decreased the deposited eggs especially at 35°C; reduced the formed cocoons and produced adults at all temperatures (15–35°C); and prolonged developmental, repriod especially at 20 or 25°C. Number of infected host larvae which allowed complete successful development for the parasitoid was significantly decreased especially at the extremes of temperatures.